The invention pertains to dispensing means for heat meltable materials.
Heat meltable materials of thermoplastic nature, such as sealants, adhesives, etc., when used in large quantities, are often packaged and shipped in bulk containers, such as 55 gallon drums. The material is packaged while hot and in liquid form and then hardens upon cooling. To permit use of such materials when packaged in drums it is necessary to heat the material sufficiently to produce a fluid state wherein the material may be readily dispensed from the drum. Usually the entire contents of the drum are not used at once and many thermoplastic heat meltable materials are adversely affected due to degradation and induced polymerization if they are sequentially heated to a melted state and then permitted to cool and reharden during periodic dispensing. Accordingly, dispensing apparatus has been devised for heating and dispensing only that material adjacent the upper surface of the shipping container and thereby heating only a relatively small portion of the packaged material at a time. U.S. Pat. No. 3,282,469; 3,412,903 and 3,637,111 disclose apparatus of this type.
While known apparatus permits limited amounts of hardened material to be transformed into the liquid state for dispensing, and thereby minimizing deterioration of the material not to be immediately dispensed, known devices withdraw the liquid material directly from the container, often adjacent a heating element. Thus, before dispensing can occur, a significant delay is incurred while the temperature of the upper surface of the thermoplastic material reaches a liquid state and, further, since the dispensed liquid material is drawn directly from the container, the dispensing apparatus is rendered inoperable when the dispensing head is removed from the depleted container and prior to a new container of heat meltable material being available for dispensing.
As the dispensing apparatus in accord with the invention may be utilized in a production line environment, a plurality of dispensing devices may be necessary in order to assure an available supply of heat meltable material at all times, thus necessitating an expensive duplication of apparatus.
Further, known dispensing apparatus of the above heat meltable material type nas not been available for use with relatively small containers, such as of 5 gallon capacity, wherein relatively continuous dispensing is possible, and while the smaller size dispensing apparatus is very attractive to the user of limited quantities of heat meltable materials or wherein a variety of material compositions are being used, the disadvantages of interruptions due to delays arising from changing from a depleted to a filled container adversely affected the economic advantages of previous dispensing apparatus of smaller capacities.